"the article was really written in collaboration with Dr. Gabe Gooding (who is a senior scientist at the University of Western Australia) and who, with her mother, Mrs. Jean Gooding, has been breeding English Cockers (under the "Yunbeai" prefix http://www.yunbeai.com/) for over 50 years now"

While the thoughts expressed in this Article are mine and I must therefore take the blame for any mistakes made, they have been developed in consultation and conversation with a number of well-established breeders both within and outside North America. These breeders are concerned with the view, stridently expressed by some, that Optigen A status is an essential part of responsible breeding. This is a view which I believe arises out of a misunderstanding of the place
such tests should take in a breeding program and a blind acceptance of the value of such tests.

As many of you know, at the General Meeting of the ECSCA which was held some years ago and at which questions were raised such as the mandatory publication of the results obtained by Optigen in tests carried out on members’ EC’s, I urged that we proceed with a degree of caution. That was a viewpoint which arose from my experience as a solicitor that, all too often, products are rushed into the market by commercial ventures, it being well established commercial reality that there is a tremendous advantage to be first in the market with a product, and that, not infrequently, this “rush to the market” approach results in the marketing of a product which is less than reliable. I expressed that viewpoint purely as a general view on new commercial products and without any particular reference to Optigen or its product.

In the time that has passed since that general meeting of the ECSCA, a number of dogs have been tested by Optigen and duly classified as “A” (completely clear), “B” (carriers) or “C” (afflicted). One very worrying matter was the apparent lack of correlation between Optigen C’s and (based on anecdotal evidence) clinically blind dogs, especially in solids. Because of this, I (and, I believe, several others) awaited the publication by Optigen, of the research on which its tests were based, in the belief that if that research was published in a publication of good repute, it could be peer reviewed by scientists qualified so to do. What happened a few years later was Optigen’s offer to re-test animals which they had previously tested and classified. Those re-tests resulted, at least in some cases, in animals being completely re-classified so that, again in some cases, EC’s classified as C’s (i.e., afflicted) came back on re-testing as A-1’s (completely clear). What was the reason for this change? At very least, it was an admission by Optigen that it’s earlier tests were less than reliable. Then, fairly recently, the ECSCA web-site contained a press release purportedly by Optigen, in which it was claimed that the actual gene for prcd/PRA had been identified, rendering even more important the validation of the Optigen test by the all-important peer review process; however, as of the time of the preparation of this article, Optigen has not published its research. This has led to more unease on the part of a not inconsiderable number of breeders with whom I have spoken, on whether they should or should not have their dogs tested.

There is, of course, always the question of the costs involved (and who in the business of breeding and showing dogs these days is unaware of the costs)! But perhaps more significant is the question of how much importance one should attach to the results of such tests. There was the “flare up” which, I believe first focused breeders’ attention on prcd/PRA in the early to mid ‘Sixties, when one or more dogs in the United Kingdom, including Mrs. Doreen Robertson’s beautiful blue Nostrebor Neopolitan, were withdrawn from public stud because of the problem, after which the problem seemed to “fade away”; there was the rise in the late ‘Eighties in North America, when another “wave” of clinical prcd/PRA seemed to erupt, and that also seemed to fade away. Apart from these “peaks”, although prcd/PRA has been with us, it does not seem to have been a significant problem in our breed. Also, we have some time now, had the benefit of the expertise of veterinary ophthalmologists, and of ERG’s, methods which have served us well in detecting the few cases of the problem in our breed.

I do not know of any facts which indicate that the incidence of prcd/PRA in our breed, has since changed. Recent enquiries to several leading breeders – some of partis and some of solids – would appear to indicate that the incidence of clinical prcd/PRA is still small. Even breeders who have been in the game for many years and have over that time bred goodly numbers (in the region of several hundred), have indicated that, to the best of their knowledge, they have had, if any, a single or perhaps two or 3 dogs which have gone blind with what was diagnosed as clinical prcd/PRA. Admittedly, these breeders have not been able to follow every pup they have bred, but I submit that it is a reasonable expectation that if a significant number of the stock sold had gone blind, at least SOME the purchasers would have complained. This brings me to my first (and perhaps most important) point. What is new is not a rise in the incidence of prcd/PRA, but only a new, and perhaps more accurate method of examining our EC’s for the same. THE BREED IS NOT FACING A CRISIS, and I would urge all breeders not to act precipitously. Although prcd/PRA is clearly something of which we should be aware and avoid if possible, it is not to be compared with, say, Familiar Nephropathy (“FN”) which is a fatal condition and in which, so I am informed, the animal would die in great distress unless put down.

In June, 2005, an announcement was made that Optigen had now located the actual gene responsible for prcd/PRA. This claim could only have substance if it applied to the whole of the breed, i.e. that this particular gene was responsible for prcd/PRA in both solids and partis. There was, however, a difficulty: if this gene is responsible for the condition in all EC’s, then how was one to explain the fact that in one subgroup (partis) the condition expressed itself early (2-4 years), whereas in another subgroup (solids) of EC’s carrying the same relevant gene structure, the expression was very different in that its was late (7-8 years) and its members in some cases, died as sighted dogs, i.e., never exhibited clinical signs of prcd/PRA. As I understand Optigen’s statement, they attribute this difference, i.e., the difference in the manifestation of clinical prcd/PRA in the two groups, to the presence, in one group, of another gene (which, for the sake of convenience, I will term “the Interfering Gene”). To quote the Optigen press release of June 1 2005 (as it appears in the ECSCA web page):
“We have also retested the pedigrees of extremely late onset PRA, that had multiple members testing as Pattern C1. All of the C1 dogs are “Affected” with the mutation test. That leaves us with the theory that this subgroup inherits prcd-PRA but also must inherit an unidentified second gene that modifies the onset of PRA, causing some “Affecteds” in the pedigree to exhibit typical prcd-PRA, and some retain good vision throughout their lifetime. Unfortunately, we do not have any more satisfying explanation for the situation. Hopefully it will be more clear with ongoing research.”

Although Optigen does not identify the two groups as partis and solids, I believe that, generally speaking, the experience of most of us is that the two groups or subgroups are indeed partis and solids, and for ease of reference, that is how I propose to refer to them in this article. If the number of cases of the condition in partis can fairly be characterized as being small, it has, in solids through all this time, been minimal. Certainly my own experience as a breeder of (mainly) solids, confirms this: as have many breeders, I have, over the years, frequently had my dogs’ eyes examined by qualified veterinary ophthalmologists. I can only recall having one blind EC in my stock, over what is now over 45 years in the breed, and his condition was professionally diagnosed as being the result of diabetic cataracts. This difference in expression of the condition in partis and solids, has been a puzzling factor, because both partis and solids come from the same root stock - the practice of breeding partis only to partis and solids only to solids, is a fairly recent innovation – and one would not, therefore, expect a different genetic makeup in coloured dogs as compared to solids. If one goes back to the ‘Fifties and even more in the “Forties, what we nowadays term “cross-colour breeding” was not at all uncommon.

There are several possible explanations for the difference in the clinical manifestation of prcd/PRA in partis and solids, including the following:

that Optigen has correctly identified the gene, but that (as Optigen seems to believe), solids “inherit an unidentified second gene that modifies the onset of PRA, causing some .. to exhibit typical prcd-PRA, and some retain good vision throughout their lifetime”;

that the gene which Optigen believes is responsible for prcd/PRA is in fact not the gene responsible; and

that Optigen has correctly identified the gene, but that it is the early developers (partis) which have “an unidentified second gene that modifies the onset of PRA”, rather than solids. In other words, rather than “interfering” to delay (or completely block) the onset (in solids), the postulated second gene “augments” or accelerates the deterioration in the retina of affected dogs (partis), i.e., the reverse of the suggestion by Optigen. Is there any possible basis for this third theory? Prcd/PRA is apparently the same condition as Retinitis Pigmentosa in humans - it has been described as “…phenotypically the canine counterpart of retinitis pigmentosa (RP) in humans….” (see Acland et al, “Linkage Analysis and Comparative Mapping of Canine Progressive Rod-Cone Degeneration (prcd) Establishes Potential Locus Homology with Retinitis Pigmentosa (RP 17) in Humans” (Proc. Natl. Acad. Sci U.S.A. 95: 3048-3053, 1998). In Retinitis Pigmentosa, blindness is caused by abnormalities in the pigment layer of the retina. If indeed prcd/PRA is “phenotypically the canine counterpart of retinitis pigmentosa”, and since it is known that the R (= Roaning) and T (= Ticking) genes (in partis) are involved in the pigmentation process (at least of the coat), might those R and T genes not somehow be involved, either in the pigment layer of the retina, or in some other way? This idea was expressed to me by a friend who is an experienced scientist in the biological field and who has been involved in the breeding of EC’s for a very long time. It is, of course, purely a theory, and there is no evidence to establish that this theory is correct, but it is at least as plausible as the contrary theory that solids carry the Interfering Gene. The importance of this theory is that, if it is correct, the prcd/PRA gene as identified by Optigen is of itself relatively harmless in that, if it expresses itself at all, it does so late and in a very small number of dogs. It also explains the differences in expression of prcd/PRA between coloured and solid EC’s without having to postulate the existence of the “Interfering Gene” (which in my view is unlikely, bearing in mind the common ancestry of the two colours)

Let us assume, however, that Optigen’s hypothesis is correct – that there is an Interfering Gene in solids. How does one explain the fact that a good number (if not most) solids which test as Optigen C‘s, remain sighted throughout their lifetime? One explanation that has been related to me, is that if those dogs lived long enough, they would indeed go blind! This is obviously something incapable of being proven right or wrong, and is therefore more properly consigned to the realm of speculation. “Explanations” of this type are, to my mind, completely detached from the reality which we, as breeders, have to deal with, and as such, are without value. In any event, all living systems suffer the ravages of time, and if the retina (or any other part, for that matter) of an EC of 12 or 13 years of age starts to deteriorate, that is not something which, I suggest, should be unexpected.

I would also question the actual predictive value of the test for Optigen C classified dogs, i.e., how many C classified dogs have in fact developed the condition within their normal life span and what proportion of C classified dogs can we confidently predict will develop the condition? I have seen no statistics on this point, but clearly (as Optigen appears to agree) there are a number of cases where C classified dogs do NOT develop the condition, and more research needs to be on this point before the value of the Optigen test can be properly established..

There are additional questions. Is it possible that, in many situations in which an EC passes on the prcd/PRA gene, it also passes on the Interfering Gene (i.e., that in those EC’s, these two genes sort of go in tandem, that there is some sort of “linkage” here )? If the Interfering Gene is often linked with the prcd/PRA gene, this would clearly diminish the significance of the prcd/PRA gene (and the corresponding Optigen C classification) in a breeding program.

I also question the wisdom of proceeding headlong into this field of the testing offered by Optigen, on the basis of the present science. If Optigen is correct and an Interfering Gene exists, or if the expression of the prcd/PRA gene is somehow dependant on some other factor, such as linkage, or the augmenting action of the R and T genes mentioned above, then, by definition, prcd/PRA is polygenic in origin, and not a simple autosomal recessive. Conditions which are polygenic in origin, are problematical. In the publication “Reproduction in Domestic Animals, Vo. 38, issue 1, page 73 – February 2003, headed “Ethics and Genetic Selection in Purebred Dogs”, V.N. Meyers-Wellen states:
“When we understand polygenic inheritance, we can potentially eliminate whole groups of deleterious genes from populations …. however, until we have enough information on gene interaction, we will not know whether some of these genes have other functions that we wish to retain. And, other population affects should not be ignored. At least initially it may be best to use this new genetic information to avoid mating combinations that we know will produce affected animals, rather than to eliminate whole groups of genes from a population. This is particularly important for breeds with small gene pools, where it is difficult to maintain genetic diversity.
Finally, we will have enough information about canine gene function to select for specific genes encoding desirable traits and increase their frequencies in a population. This is similar to breeding practices that have been applied to animals for hundreds of years …. This has great potential to improve the health of the dog population as a whole. However, if we or our breeder clients make an error, we can inadvertently cause harm through massive, rapid selection. Therefore, we should probably not be advising clients on polygenic traits or recommend large scale changes in gene frequencies in populations until much more knowledge of gene interaction is obtained.”
(emphasis mine)

I feel that the above advice is something we all should heed. It is certainly axiomatic that we should certainly avoid combinations which we know will produce blind animals – and I believe that every responsible breeder of EC’s does that - but we should not be rushing headlong into a situation which could have undesirable results for our breed as a whole.

The primary aim of a good EC breeder, MUST be to breed good EC’s. Many are the factors which go into the selection of stud dogs and brood bitches. Even assuming 100% accuracy, the Optigen tests are only determinative for a single (out of many) factors which should be considered. It is to be remembered that all Optigen claims to do, is to be able to identify the gene responsible for prcd/PRA. It would be completely incorrect, and unfair to Optigen, to read any Optigen result as doing anything more than that. Even just considering the eye (and what about the rest of the dog!), there are many other parts of the eye which could be subject to one or more genetic defects. It is fairly well established that in dogs, senile changes and degradation in the eye starts at about 7 years. Of what use is a perfect retina if the function of the eye degrades by reason of, for instance, changes in the anterior chamber?

On a related point: in 1998, Dr. David Huntsman of the British Columbia Cancer Agency identified a gene (the E–Cadherin gene) in a certain family. In its normal function, this gene produces the “glue” which holds cells together. The mutated gene, however, also causes stomach cancer. Obviously, one couldn’t just try to get rid of the gene (otherwise the patient’s cells would just fall apart), and the only recourse in the case of persons carrying the mutated gene, was prophylactic surgical removal of the stomach. As Meyers-Wellen has stated, genes sometimes have more than one function, and until we know for sure ALL of the functions of that gene, it is dangerous to breed to eliminate it. Obviously, if the gene which, in its mutated form produces prcd/PRA in EC’s, also performs some desirable function, that desirable function could not be one which is central to the maintenance of life (as is the case in the E-Cadherin gene), but it is theoretically possible that it performs some desirable but less essential function. However, Meyers-Wellen’s advice quoted advice still applies.

There is a place for genetic testing in dog breeding, but I believe that all tests must, before widespread application in a breeding program, be subject to close scrutiny, and, until they have passed that test, must be approached with a degree of caution. Even after passing that test, they should only be used sensibly. In particular, the general advice not to “throw the baby out with the bathwater” ALWAYS applies except, of course, in the case of fatal inherited conditions such as FN. I repeat that our objective, as breeders of EC’s, must always be to breed better EC’s, and a genetic problem with one aspect or another of any particular animal – whether of hips, eyes, or anything else - or family of animals, must always be considered in the context of that pre-eminent objective of a good breeder, which is to breed better English Cockers. A sound retina is only ONE feature. A mongrel with sound retinas does not a Cocker make. No single feature should be elevated above the general requirements of our wonderful breed – a short, compact, sound moving, happy little dog with lovely head, and an eye, expression and temperament which continually say “I love you.”

In conclusion, my view is that breeders should “make haste slowly” on this question. Optigen has given us a tool, and probably a useful tool, to perhaps get rid of a problem, and not a very widespread problem at that – but use of that tool must be considered in the context of all the other things which need to be considered in order to breed EC’s of good type, soundness and temperament. Let’s not go overboard with this, but approach the whole issue with some common sense! If you have dogs which are going blind, or come from lines which you know have produced blind dogs, by all means use the tool which Optigen has provided if you are satisfied with the science and its value to your breeding program. However, I take the strongest issue with those who would preach that genetic testing for prcd/PRA is somehow a necessary part of good breeding, or that Optigen C dogs should not be bred from, or that only Optigen A dogs should be bred to. Genetic testing for prcd/PRA is, at best, only in its infancy, and can only constitute a very small part of the many factors which should be considered by good breeders.

"I thought that the attached article, which I have written following upon the recently published findings (by the Animal Health Trust (U.K.) and the University of Missouri) on PRA in the English Springer Spaniel, might be of interest to Cocker breeders in Scandinavia. I have written this article on the basis that, in light of the common ancestry of the Springer and the Cocker, these findings are likely to be applicable to the Cocker."

/Eugene Phoa

WHITHER NOW, PRA TESTING?

The recent University of Missouri and the Animal Health Trust, U. K. (together referred to as “UM/AHT”) announcement (“UM/AHT Announcement”) regarding findings concerning PRA in English Springer Spaniels (“ESS”), have only served to emphasize how premature it was for breeders to jump on the Optigen bandwagon. It was, of course, the hope of those availing themselves of the Optigen test, that by breeding two English Cockers (“ECS”) found to be clear by Optigen (classified Optigen A1) they would be guaranteed not to produce any offspring with the disease.

Because some conditions appear to be very breed specific, it may be dangerous to extend the results of research on one breed, to another breed. However, one might well be forgiven for quickly making the jump from the ESS to the ECS as, not too very long ago, the two were one breed, and, as the old breeders tell us, in any given litter, the bigger pups were registered as ESS, and the smaller ones as ECS.

The University of Missouri has indicated a great interest in researching PRA in ECS, and has asked that ECS breeders with clinically afflicted dogs please send in blood samples to them, which they will then analyze. I understand that for the ESS, their charge is $40.00, with a discount of $10.00 if the blood sample is already with their bloodbank and a further $10.00 if the animal has been CERF’ed and the CERF report is sent to them. I would expect a similar charge schedule to apply to ECS, and suggest that it would be of advantage to our breed for breeders to take advantage of this offer.

Assuming that this research on ESS can validly be extrapolated to ECS (and all my views as stated in this article are based on that assumption), what does it say about the present state of PRA genetic testing on our breed? The main assumption, widely held by those breeders of ECS who have subscribed to the Optigen test, is that if an ECS is classified as OPTIGEN A1, it will not get, nor will be able to, pass on PRA. Unfortunately, it appears that this proposition is not true. My reasons for saying this are as follows:
the UM/AHT Announcement refers to the gene mutation which appears to be responsible for the PRA cases it investigated, as “Cord 1”. To my telephone enquiry, Dr. Gary Johnson (who leads the investigative team for this project at the University of Missouri) informed me that the likelihood was that the Cord 1 mutation was a different mutation from that which has been identified by Optigen. It appears to me that this is very likely accurate: as mentioned below, published results regularly indicate an Optigen C1 incidence of around 10%, whereas the UM/AHT research shows “42% tested as genetically affected.” Assuming the validity of both the Optigen and the UM/AHT research, this disparity would, I submit, tend (in the absence of other factors) to the conclusion that the 2 research teams have identified different mutations;
the UM/AHT Announcement also states that whereas the majority of the PRA cases it investigated were caused by the Cord 1 mutation:
“a second rare form of PRA may account for the 5% English Springer Spaniels with PRA that do not test “affected.”

In other words, the UM/AHT Announcement posits the existence of at least 2 forms of PRA. What breeders are left with, therefore, is that, assuming the validity of the work by UM/AHT and Optigen, there may be at least THREE possible gene mutations responsible for different forms of PRA and possibly more. And that is only what has been found so far. Will more mutations – and more forms of PRA - be discovered as the research goes on?
This analysis is consistent with Optigen’s own statement (on their website):
“Regarding PRA, we believe there is more than one form of inherited PRA in some breeds. While the prcd form of PRA (detected by OptiGen's test) is by far the cause of the majority of PRA cases, a small portion remains unidentified”

Drs. Aguirre and Acland acknowledged this fact as far back as 1988 when they stated that phenotypic differences between PRA (prcd) in miniature poodles and cocker spaniels …

“may be ascribable to different genetic backgrounds in the two breeds, reflecting the effect of modifying genes, or may indicate separate, allelic, mutations at the same locus.”
(Aguirre G.D., and Acland, G.M., Variation in retinal degeneration phenotype inherited at the prcd locus, Exp Eye Res. 46(5):663-87, 1988 May)

One notes that Optigen believes that the gene mutation it has identified “is by far the cause of the majority of PRA cases” in ECS. Similarly, the UM/AHT team believes that the Cord 1 mutation is responsible for the majority of PRA cases in the ESS. Does that mean the UM/AHT research cannot be validly extrapolated to ECS? Perhaps it does, but if, in light of the common ancestry of theses two breeds, such extrapolation is valid, breeders are left with even more uncertainty as to which gene is causing the majority of PRA cases. One thing is clear: even assuming a 100% validity for Optigen’s claims, an Optigen A1 classification is no guarantee that the animal will not get or pass on another form of PRA as it, at best, only identifies one of the gene mutations which could possibly cause the condition.

As our members know, questions were raised some time ago as to why Optigen C1 (i.e., genetically afflicted) solid ECS frequently did not show signs of blindness (if at all), until well on in years (i.e., late-onset), with some never showing signs of blindness and eventually dying fully sighted. Optigen posited the existence of some gene which somehow interfered with the deleterious action of their mutation in a particular “subgroup” of the breed (i.e., solids) . The UM/AHT group has made a similar finding with respect to ESS, as they state:
“Dogs which are DNA tested as being affected may themselves not develop the disease until relatively late in life, but it may well be possible for offspring … to display …an earlier …form of PRA depending on other genetic variants that they do or do not inherit.”

What is interesting is that the ESS do not have a solid/particolour division - the ESS are ALL partis. It therefore appears that the late-onset phenomenon is not necessarily colour related. Does this mean that the late (or no) onset phenomenon is something that has been present in the ancient gene pool (i.e. common to breed before it split into ESS and ECS), and is present not only in solid ECS but in partis as well? Further research is clearly necessary.

The UM/AHT Announcement also states that:
“Additional research is being carried out to help us understand why some genetically affected dogs develop PRA early and other later. This research is likely to take some time.”

Without in any way disagreeing with that statement, one cannot run away from the conclusion that we are still a long way from a test which will accurately predict whether or not ECS found clear by the available genetic tests, will or will not produce PRA if bred together. This is emphasized by the following:

Optigen regularly publishes figures indicating that the number of ECS found afflicted by their test (i.e., Optigen C1) is in the region of 10% of all tested dogs, whereas the actual number of clinical cases is far, far lower – something less than 1%. If one assumes that an Optigen C1 classification is supposed to be predictive of clinical PRA, then what one ends up with is that the Optigen test is, at very least, giving a false clinical positive within the life span of the dog, NINE TIMES OUT OF TEN. If the Optigen test is not supposed to be predictive of clinical PRA, then what is its value; and I would also ask whether breeders should be giving a test which gives this large number of false positives, any real prominence in their breeding programmes?

the UM/AHT Announcement states that they have found that:
“In the USA, only 20% of the 1100-plus ESS ‘s genotyped during the research tested as clear or normal. 38% tested as carriers, and 42% tested as genetically affected.”
Although I do not have any figures as to the number of ESS clinically afflicted by PRA, it is my understanding that it is well below 1%, and if that is the case, then, for the ESS, the predictive value of the UM/AHT test is even less than that of Optigen’s, though I hasten to point out that the UM/AHT team does not appear to claim much more than to say that “Wise use of this test can reduce the incidence of dogs at risk for PRA in future generations.

The UM/AHT Announcement makes the following recommendations:
“A realistic approach when considering which English Springer Spaniels to select for breeding would be to consider dogs with the mutation to have a fault just as lack of working ability, poor top line, or imperfect gait would be considered faults.
Dogs that test ‘affected’ with two mutant copies of the PRA gene should be considered to have a worse fault than ‘carriers’ with only one mutant copy. English Springer Spaniel breeders could then continue to do what conscientious breeders have always done: make their selections for breeding stock in light of all of the dogs’ good points and all of the dogs’ faults. Using this approach over several generations should substantially reduce the prevalence of PRA while continuing to maintain or improve those qualities that have made English Springer Spaniels so popular.”

I suggest that the general thrust of the above recommendation makes eminent good sense; however, I would hesitate to apply it on the basis of dogs which are tested to have or not have the mutation, but would instead apply it to clinically afflicted or clinically not afflicted dogs, for the following reasons:

at least until we know more about what this – or any other gene - does (in addition to rod/cone degeneration), it is dangerous to breed to exclude it. I have raised this issue before. Mutations are a natural part of the evolutionary process, and are not infrequently responses to challenges to the organism. It is not unknown for a certain gene to have more than a single function, and until we know exactly what else any gene might do, I would suggest that to propose breeding it out, may have unexpected and undesired effects on our breed.

if we select on the basis of excluding clinically blind animals, rather than on those with either 1 or 2 copies of the mutation, we will be selecting on a gross basis, i.e., not only on the perceived expression of the mutation itself, but also on its overall effect having regard to other factors which may affect the expression of the mutation. I recently read some post from one of the YAHOO groups which was kindly forwarded to me by an established and respected breeder of ECS, in which Joan Beck, states:
“We do know that only a small percentage of mutations cause genetic disorders – most have no impact on health or development. For example, some mutations alter a gene’s DNA base sequence but do not change the function of the protein made by the gene.
We also know that some gene mutations that can cause a genetic disorder are repaired by certain enzymes before the gene is expressed (makes a protein). Each cell has a number of pathways through which enzymes recognize and repair mistakes in DNA. Because DNA can be damaged or mutated in many ways, DNA repair is an important process by which the body protects itself from disease. Perhaps the rest of the answer to the PRA question lies along these lines.”

As I see it, if a dog has 2 copies of the gene mutation but is NOT clinically blind, the chances are that that dog has the ability to somehow counteract the harmful effects of that mutation. If that dog is also able to pass that ability on to its offspring, is that not, in the ultimate analysis, what we should be looking for, at very least until we know that the mutation in question does not also carry out some other (desirable and perhaps, very useful) function which we would want to preserve? And is selecting on the basis of these gross effects not what responsible breeders have been doing all the time, anyway?

A long time breeder,Ms. G. Gooding in Australia, whose opinion I respect and who is scientist in one of the biological sciences, recently expressed to me the view that: “it appears that the research is getting close to the position that PRA … may be an extremely complex condition which is not the result of a single mutation. Perhaps a single mutation increases the likelihood of developing the disease but a complex suite of circumstances needs to exist before the condition actually manifests itself in the dog.”

I realize that I will sound to some as if I am against genetic testing; I emphasize that I am not. What I hope I am doing is to look at the genetic testing bandwagon critically, and to suggest that one must be slow to take steps which might at first blush appear to be of advantage to the breed, but which may prove not to be the case as further research is done. It saddens me that some breeders appear to be using the available PRA genetic testing as the only – or at least, the main - benchmark in their breeding programmes, so that superior dogs which grade as Optigen B1 have been passed over in favour of dogs of less merit which have graded Optigen A1 (I hasten to add that I have not had any of my own dogs tested by Optigen, so this does not concern me directly). This is, of course, contrary to Optigen’s own recommendation that dogs graded Optigen B be used, and can only result in a lowering of breed quality generally. Genetic research should be encouraged, but it appears to me that this aspect of PRA testing is, at present, very much in its infancy, and a lot more research should be done before breeders use the PRA genetic testing in their breeding plans, in any determinative way.